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We describe the analysis of in-situ HT-XRD data of a dual phase stainless steel exposed to a complex thermal cycle of heating, holding and cooling. For the conditions used only low quality diffraction data could be collected. Peak positions, peak areas and peak broadening are modeled by the Rietveld method. The low signal-to noise ratio and the presence of artificial peaks due to tube tails complicate the data evaluation. In a first attempt the parameters are refined by a local optimization procedure (e.g. Levenberg-Marquardt). However, this procedure fails by being caught in one of several local minima. Next, a Bayesian approach with a Markov Chain Monte Carlo (MCMC) algorithm is used as a global optimization procedure to refine the simulated Rietveld diffractograms. Accurate estimates of the evolution of the phase fractions and dislocation densities in martensite and austenite during all stages of the thermal cycle are obtained by this MCMC algorithm. While an approach based on multivariate second order Taylor series completely underestimates the error, the uncertainties in the model parameters could be estimated appropriately from histograms obtained by the MCMC method.

Thermodynamic data of various crystalline solids are assessed from low temperature heat capacity measurements, i.e., from almost absolute zero to 300 K by means of semi-empirical models. Previous studies frequently present fit functions with a large amount of coefficients resulting in almost perfect agreement with experimental data. It is, however, pointed out in this work that special care is required to avoid overfitting. Apart from anomalies like phase transformations, it is likely that data from calorimetric measurements can be fitted by a relatively simple Debye–Einstein integral with sufficient precision. Thereby, reliable values for the heat capacities, standard enthalpies, and standard entropies at T = 298.15 K are obtained. Standard thermodynamic functions of various compounds strongly differing in the number of atoms in the formula unit can be derived from this fitting procedure and are compared to the results of previous fitting procedures. The residuals are of course larger when the Debye–Einstein integral is applied instead of using a high number of fit coefficients or connected splines, but the semi-empiric fit coefficients keep their meaning with respect to physics. It is suggested to use the Debye–Einstein integral fit as a standard method to describe heat capacities in the range between 0 and 300 K so that the derived thermodynamic functions are obtained on the same theory-related semi-empiric basis. Additional fitting is recommended when a precise description for data at ultra-low temperatures (0–20 K) is requested. Graphical abstract

The deflection (curvature) of embedded single-crystal silicon chips was investigated by rocking curve X-ray diffraction techniques at two significant manufacturing stages in the process chain of printed circuit boards with embedded components. An overview of the curvature deduction by two different approaches was presented: (1) the measurement of the variation of the rocking curve maximum as a function of the lateral sample position along a specific traverse; the slope in such a diagram is then proportional to the corresponding curvature in that direction. (2) The evaluation of the rocking curve width; here the peak width is inversely proportional to the curvature at known beam diameter, diffraction angle, and beam divergence. It was shown that the rocking curve method is applicable to determine the curvature inside single crystalline chips. Furthermore, the method is also suitable to determine the curvature of fully embedded or encapsulated chips. Additionally the absorption of the radiation in the embed medium was quantitatively discussed. The curvature of two different prepared samples was determined at temperatures up to 200 °C in a heating stage attached to the diffractometer device.

Dilatometric studies assisted by high-temperature laser scanning confocal microscopy provide a comprehensive experimental picture with regard to cyclic austenite-to-ferrite transformations in Fe–C alloys. The validity range for the sharp interface and effective mobility approach is identified by comparing modelling results with calculations based on experiments. The interface velocity for the austenite-to-ferrite transformation in pure iron is exclusively controlled by the intrinsic interface mobility conforming to the upper boundary of mobilities. The austenite-to-ferrite transformation in Fe–C alloys under conventional cooling and heating conditions is primarily controlled by carbon diffusion in austenite. The lower boundary of the temperature-dependent interface mobility has been established for an Fe–C alloy over a wide range of temperatures during cycling transformation. Austenite-to-ferrite transformations in Fe–C–X alloys are characterized by still lower effective mobilities depending on both tempe...

The stability of austenite is one of the most dominant factors affecting the toughness properties of high Co-Ni steels such as Aermet 100 and AF1410. Thus, the aim of this work was to get a deeper understanding on the impact of combined heat and cryogenic treatment on the stability of retained and reverted austenite. In order to characterize the evolution of the phase fraction of austenite during tempering at different temperatures and times, X-ray diffraction analyses were carried out. The stability of austenite, which was formed during tempering, was analyzed with dilatometric investigations by studying the transformation behavior of the austenite during cooling from tempering temperature down to −100°C. Additionally, transmission electron microscopy investigations were performed to characterize the chemical composition and phase distribution of austenite and martensite before and after tempering.

Three-dimensional electron backscatter diffraction, focused ion beam, transmission electron microscopy and energy filtered transmission electron microscopy were employed to investigate the structural information of primary Al{sub 3}(Sc,Zr) phase, i.e. size, shape, element distribution and orientation relationship with the α-Al matrix. It was found that (i) most primary Al{sub 3}(Sc,Zr) phases have a cubic three-dimensional morphology, with a size of about 6–10 μm, (ii) most primary Al{sub 3}(Sc,Zr) phases are located within the α-Al matrix, and exhibit a cube to cube orientation relationship with the α-Al matrix, and (iii) a layer by layer growth was observed within primary Al{sub 3}(Sc,Zr) phases. Al, Cu, Si and Fe are enriched in the α-Al matrix between the layers of cellular eutectic Al{sub 3}(Sc,Zr) phase, while Sc, Ti and Zr are enriched in small Al{sub 3}(Sc,Zr) phases. A peritectic reaction and subsequent eutectic reaction between Al{sub 3}Sc and Al was proposed to interpret the observed layer by layer growth. This paper demonstrates that the presence of impurities (Fe, Si, Cu, Ti) in the diffusion field surrounding the growing Al{sub 3}(Sc,Zr) particle enhances the heterogeneous nucleation of Al{sub 3}(Sc,Zr) phases. - Highlights: • Most fine cubic primary Al{sub 3}(Sc,Zr) phases were observed within the α-Al matrix.more » • A layer by layer growth within primary Al{sub 3}(Sc,Zr) phase was observed. • A peritectic and subsequent eutectic reaction between Al{sub 3}Sc and Al was proposed. • Impurities in diffusion fields enhance heterogeneous nucleation of Al{sub 3}(Sc,Zr)« less

The aim of this study was to analyze the influence of combined heat and cryogenic treatment on the evolution of martensite and reverted austenite in a high Co-Ni steel. To this end the evolution of phase fractions and lattice constants after thermal treatments were characterized by using X-ray diffraction (XRD) investigations and dilatometer analyses. The arrangement of phases and the element distribution in martensite, austenite and carbides were analyzed by using energy filtered transmission electron microscopy (EFTEM).

The application of the Rietveld method for lattice constant and crystal structure refinement has been undertaken with great success. More routinely, this method is used to estimate quantitative phase amounts and to get information on the coherent diffracting length and the lattice defect density. In this paper an innovative combination of the Rietveld method with the Bayes approach is presented, to obtain directly the distribution of the refined parameters from a measured diffractogram, while the conventional Rietveld technique enables only the deduction of the most probable parameter and the estimation of its precision by confidence intervals. Furthermore, the goal of this work is to promote the development of a robust and automatable Rietveld algorithm. A detailed description of the modified algorithm is presented. Such a modified Rietveld approach is applied to anin situhigh-temperature experiment on a steel sample, including the temperature-dependent α → γ phase transformation reaction during heating and the martensitic transformation during the cooling phase.

The presented X-ray diffraction techniques enable the simultaneous characterization of phase content, dislocation densities in the austenitic and the ferritic/bainitic/martensitic phases, or the tetragonal lattice distortion and the interstitial carbon content in martensite. The capability of the diffraction methods is demonstrated using the example of heat treatment of high speed steels.

Chromium nitride/titanium–titanium carbonitride multilayers composed of a 40 nm Cr interface followed by a 4.4 μm thick Cr2N layer, a 150 nm thick Ti layer, and a 1 μm thick TiCxNy top layer were deposited on silicon wafers by magnetron sputtering. The structural changes and the phase content changes of these multilayer samples were studied by means of high-temperature in-situ X-ray diffraction experiments at temperatures up to 550 °C. The lattice constants of the Cr phase as well as the Ti phase display an aberrant expansion behaviour during these experiments which is influenced by the defect structure, a nitrogen incorporation, and residual stress in the layers. The results were compared with structural data obtained by ex-situ transmission electron microscopy investigations of pristine and heated material, revealing phase separation and strong diffusion phenomena.

Chromium/chromium nitride multilayer coatings consisting of a stack of alternating 82 nm thick chromium and 168 nm thick CrNx sublayers with a total thickness of 4 μm were deposited on silicon wafers by magnetron sputtering below 70 °C. X-ray diffraction revealed for the as-deposited state a significant fraction of material in amorphous state. The effect of subsequent heat treatment on the formation of the crystalline phases Cr and Cr2N, on the coherent diffracting length of the occurring crystallites, as well as the correlated variations of the lattice cell parameters was studied by in-situ high temperature X-ray diffraction techniques. Ex-situ observations of the crystallographic texture showed the presence of a fibre texture parallel to the [1 0 0] direction for the Cr-phase and a fibre texture parallel to the [1 1 2] direction for the Cr2N phase.

For the investigation of retained strains during hot forming, which are related to the dislocation structure, single and double hit compression tests were carried out at different temperatures and strain rates for a stainless steel. Using microhardness measurements the retained strains after the first and second pass were investigated as a function of the amount of deformation, temperatures as well as strain rates and dwell durations. In general, the retained strain decreases with increasing dwell durations in both the deformed and recrystallized grains, respectively. At a given total amount of deformation in a double hit compression, the retained strains for the as deformed unrecrystallized grains are reduced for a lower deformation in the first hit. For the recrystallized grains the retained strain increases, when comparing double hit with single hit compression.

Double-hit compression tests were carried out at different temperatures and strain rates for a nickel based alloy and a stainless steel. Using microhardness measurements the retained strains after the first and second pass were investigated as a function of the amount of deformation, temperatures as well as strain rates and dwell durations. In general, the retained strain decreases with increasing dwell durations. It is shown that at a given total amount of deformation, the retained strain is reduced for the as deformed grains that have not been recrystallized yet, but increased for the recrystallized grains, when comparing double hit with single hit compression tests.

For the application of Fe-Co-alloys in fuel-injection systems several physical properties as saturation magnetization, permeability, remanence and the electric resistivity are the predominant parameters to achieve an optimal functionality of coil formers. These properties are achievable by a process technology which starts at the vacuum melting and a vacuum arc remelting process and is continued at the blooming and the multi line rod rolling mill and ends finally at the finishing line. The above listed properties are associated with the low carbon ferrite structure, which can be achieved by the y/a- transformation and a subsequent ferritic recrystallization. Further the homogeneity and purity of the material take a dominant role in the thermo-mechanical controlled rolling process. To stabilize the deformed ferrite structure, the alloy has small additions of Vanadium, which is precipitated strain induced as vanadium-carbo-nitride in the deformed ferrite at 750 °C. Impurities as oxides or sulphides, which act as nucleation sites for this V(C,N)-precipitation reaction, consume therefore a part of the required nucleation potential. The second purpose of the small vanadium addition, associated with the precipitation, is to reduce the solute carbon content of the ferrite structure to achieve a low magnetic remanence. To investigate these interactions, several process steps were physically simulated on a "Gleeble 3800TM" system which has been extended by a "maxstrain" unit to simulate multistep deformation sequences below the γ/α- transformation temperature. Subsequently the achieved structures were investigated by transmission electron microscopy and electron back scatter diffraction analysis. The results have been successfully transmitted to the process and confirmed by the operational results.

Controlling the growth of eutectic Si and thereby modifying the eutectic Si from flake-like to fibrous is a key factor in improving the properties of Al-Si alloys. To date, it is generally accepted that the impurity-induced twinning (IIT) mechanism and the twin plane re-entrant edge (TPRE) mechanism as well as poisoning of the TPRE mechanism are valid under certain conditions. However, IIT, TPRE or poisoning of the TPRE mechanism cannot be used to interpret all observations. Here, we report an atomic-scale experimental and theoretical investigation on the roles of Eu during the growth of eutectic Si in Al-Si alloys. Both experimental and theoretical investigations reveal three different roles: (i) the adsorption at the intersection of Si facets, inducing IIT mechanism, (ii) the adsorption at the twin plane re-entrant edge, inducing TPRE mechanism or poisoning of the TPRE mechanism and (iii) the segregation ahead of the growing Si twins, inducing a solute entrainment within eutectic Si. This investigation not only demonstrates a direct experimental support to the well-accepted poisoning of the TPRE and IIT mechanisms, but also provides a full picture about the roles of Eu atoms during the growth of eutectic Si, including the solute entrainment within eutectic Si.

Here, two Praseodymium doped ZnO multilayer varistor (MLV) samples with Ag/Pd electrodes were macroscopically and microscopically investigated. Since the varistor effect is a grain boundary effect, the electrical properties of individual ZnO grain boundaries were especial subject of this study. Both samples were cross sectioned for the AFM based investigation. Besides conductive atomic force microscopy (C-AFM), Kelvin Probe Force Microscopy (KPFM) and KPFM with a voltage applied between the varistor electrodes, so called scanning surface potential microscopy (SSPM), have been employed. Both samples were mapped with electron backscatter diffraction (EBSD) after the AFM based investigations. In C-AFM, a high conductivity of the ZnO grains and a high resistivity of the grain boundaries was proven. With SSPM, individual grain boundaries with an asymmetric electrical behavior were identified. These grain boundaries are causing asymmetric current paths and therefore can cause asymmetric device behavior.

Um dem Leser einen Uberblick uber die neuen leistungsabhangigen Besoldungselemente Leistungsstufe/Verbleiben in der Stufe zu geben, sollen zunachst die fur diese Arbeit interessanten Regelungen im Bundesbesoldungsgesetz (BBesG) angesprochen und im Anschlus die hierzu ergangenen Verordnungen der Bundesregierung28 und der Bayerischen Staatsregierung29 dargestellt werden. Dabei soll, soweit zum besseren Verstandnis erforderlich, bereits hier auf die zu den Verordnungen ergangenen Durchfuhrungshinweise des Bundesministeriums des Innern30 und des Bayerischen Staatsministeriums der Finanzen31 eingegangen werden.

Das DRRG eroffnet durch § 12b BRRG den Landern die Moglichkeit, bestimmte (statusrechtliche) Amter mit leitender Funktion zunachst nur im Beamtenverhaltnis auf Zeit zu verleihen. Im ursprunglichen Gesetzentwurf der Bundesregierung war eine derartige Ermachtigung nicht vorgesehen. Obwohl der Bundesrat davon ausging, das das damalige Rahmenrecht die Lander nicht hinderte, entsprechende Zeitbeamtenverhaltnisse zu regeln, sprach er sich fur eine explizite Ermachtigung aus, da man eine Sperrwirkung fur das Institut des Zeitbeamten fur Leitungsfunktionen befurchtete, wenn zur Vorbereitung auf die dauerhafte Ausubung einer Leitungsftmkti-on ausschlieslich die Moglichkeit des Probebeamtenverhaltnisses (§ 12a BRRG) vorgesehen wurde650. Die Bundesregierung wendet sich in ihrer Gegenauserung vor allem wegen der dadurch moglichen Gefahrdung der sachlichen und personlichen Unabhangigkeit der Beamten durch sachfremde Einflusse gegen die Einfuhrung der Vergabe von Spitzenpositionen auf Zeit. Auserdem weist sie daraufhin, das ein Zuruckfallen in das ursprungliche Amt von den Betroffenen als Degradierung empfunden werde. Dies fuhre zwangslaufig zu erheblichen Einbusen an dienstlichem Ansehen und Durchsetzungskraft. Schlieslich sei es aufgrund mangelnder freier Dienstposten schwierig, den zuruckgefallenen Beamten in einer entsprechenden (niedrigeren) Funktion zu beschaftigen651. Wie das Ergebnis zeigt, konnte sich die Bundesregierung im Vermittlungsausschus mit ihren Befurchtungen nicht durchsetzen. Der Freistaat Bayern hat von der rahmenrechtlichen Ermachtigung durch Erlas des Art. 32a BayBG Gebrauch gemacht.

Nach der eingehenden Untersuchung des neuen § 27 Abs. 3 BBesG sollen nun auch die weiteren durch das DRRG neu eingefuhrten leistungsabhangigen Bezahlungselemente Leistungspramie und -zulage naher beleuchtet werden. Zum besseren Verstandnis sollen auch hier die fur diese Arbeit interessanten Regelungen des § 42a BBesG und der Leistungspramien- und -Zulagenverordnungen des Bundes (LPZV)450 und des Freistaates Bayern (BayLPZV)451 kurz dargestellt werden, wobei auch hier erforderlichenfalls auf die entsprechenden Durchfuhrungshinweise des BMI452 und des Bayerischen Staatsministeriums der Finanzen453 eingegangen werden soll.

Miniaturised silicon-based multilayer chips are nowadays widespread as semiconductor components for the mobile device technology. The use of special processing and integration procedures requires such materials to possess a definite mechanical strength to ensure the functionality of the entire device. The strength and mechanical reliability of such components can be described by the Weibull theory, and is highly influenced by the geometry of the metallisation and other near-surface functional layers. In this work, we attempt to clarify the mechanisms leading to the failure of the metallised side of Si-chip components. The combined use of Finite Elements (FE) and Focused Ion Beam (FIB) analyses allowed recognising that cracks are induced in the metal-oxide-silicon interfacial area well before complete failure of the component. Such cracks have a crucial role in the lower strength and higher Weibull modulus observed on the metallised side.